# Progress: Explorer M2 Fix 2

Last visited: 2026-10-01T20:34:30Z
Status: Completed - Frustum Culling & Edge Cases Investigation

## Completed Steps
- [x] Initialized DISPATCH.md and BRIEFING.md
- [x] Analyzed ORIGINAL_REQUEST.md (R2), reviewer_m2_2 handoff, challenger_m2_1 handoff
- [x] Examined `tile_map_renderer.js`, `iso_math.js`, `map_render_benchmark.js`, `stress_test_lru_cache.js`
- [x] Derived exact mathematical 4-plane Separating Axis Theorem (SAT) for 2:1 isometric diamond vs screen rectangle
- [x] Empirically proved elimination of phantom chunks (drops visibleCount from 8 to 6 at (30,30) and (50,50))
- [x] Tested 61,008 chunk configurations: confirmed 0 false negatives
- [x] Solved 0x0 viewport early exit and negative coordinates / NaN / extreme pan handling
- [x] Benchmarked Lissajous 10,000 frames: average blits reduced to 5.23 (comfortably within <= 6.0 budget)
- [x] Coordinated with explorer_m2_fix_1 chunk sizing experiments (16x16 vs 8x8)
- [x] Produced comprehensive `report.md` with drop-in code snippet for Worker M2
- [x] Produced 5-component `handoff.md`
- [x] Updated persistent memory in `BRIEFING.md`
- [x] Ran hygiene audit: confirmed 100% hard cap compliance